The reading worth logging every morning is the previous day's total generation, written down at the same clock time each day before the array starts producing, with the date, the weather and the battery's lowest point overnight recorded beside it. One line per day, same fields, same order. That is the entire discipline, and it is the only thing you can do in the first weeks that you cannot do later, because the weeks before anything goes wrong are the only period you cannot reconstruct once they are gone.
I take mine at 6:40. Not because that number is special — it is simply before the kettle, before the shower, and after the app has finished counting yesterday. Coffee in one hand, phone propped against the fruit bowl, notebook open on the counter with yesterday's line still visible above the empty one. Four things go in, always in the same sequence: the previous day's total, the date, the weather in words, and two battery numbers. That's it. Ninety seconds, and the day is logged.
Most people open the app a dozen times a day in the first fortnight and write nothing down. I did that too. It feels like monitoring. It isn't. Scrolling a graph makes you feel informed without leaving anything behind that a future version of you can argue with.
Why the same clock time matters more than the number
A solar array is a sunlight machine, which means almost every number on that screen is a moving target. If I read the live power figure at 9am on a clear day and again at 4pm on a cloudy one, I have learned nothing except that the weather changes. The clock is the only variable I actually control. Fix it, and the weather becomes the thing that moves — which is exactly what I want, because weather is visible and I have written it down.
Reading the previous day's completed total rather than today's live power is the second half of the same idea. A completed day is a whole day. A live figure is a snapshot of whatever the house happened to be doing at that second, and if the geyser kicked in, the snapshot drops and I panic about nothing.
The number only means something next to the installer's estimate
On the commissioning paperwork there is a range — what that specific array, on that specific roof, at that tilt, in this province, was projected to produce across a year. That estimate is the only thing my daily line has anyone to talk to. It is the comparison that shows whether soiling, a shadow that arrives at four in the afternoon off the neighbour's tree, or a string that never quite woke up is quietly shaving output off every single day.
In week one I write the number down and do nothing about it. A shortfall that appears once is weather. A shortfall that appears eight days out of ten, in the same weather, is a pattern — and by then I have the eight days on paper instead of a feeling.
What the battery column actually records
Two numbers, not one. The state of charge when the sun goes down, and the lowest it dropped before the sun came back. Over two weeks those two lines tell you whether the backup window you agreed to on the load list actually exists in the house.
Everybody signs a sensible load list on paper. Lights, fridge, television, wifi, one plug for the laptop. Then the first overcast week arrives, the household behaves like a household, and the battery tells the truth about what was really on it. If it is sitting in the low forties at six in the morning after an ordinary night, that is a fact I want written down rather than half-remembered. What to do about it is a conversation with the installer, not something I go and adjust myself.
Grid import while the grid is down
If the app or the municipal meter shows import during a load-shedding block, I log the block and the rough amount and leave it there. That is either a load heavier than the plan accounted for, or a configuration question with the installer's name on it. It belongs in the notebook mainly because it is exactly the kind of thing that gets mentioned three months later as "I think it did that once" — useless to anyone.
Data gaps are not production zeros
At some point in the first month the app will show nothing for a stretch. In my experience that is far more often a communications problem than an equipment failure, and it needs its own line. "No data, broadband down, 14:00 to 17:00" goes in a separate note, never as a zero in the production column. Log a gap as zero generation and you have taught your own baseline a lie, and you will spend a bad afternoon convinced the system has died when the wifi had a bad day.
Weather in words, not numbers
"Clear Highveld morning." "Low cloud, drizzle since yesterday." "South-easter blowing, panels still wet at seven." Words, because in six months the words are what let you say the drop started with the dust storm, instead of saying it just started. A temperature reading does not carry the same information as "the whole street was grey until ten."
Keep it somewhere boring
A note on the phone, a spreadsheet, the back of an envelope stapled to the inside of a cupboard door. It genuinely does not matter which, as long as it is one line per day and the fields never change order. I also photograph the app screen at the same moment — a photo does not guess or transpose digits.
If your inverter has no logging portal, or your prepaid meter only ever shows what you bought, you work with what you have. The record is coarser. It is still a record, and it is still worth more than the memory of a graph you scrolled past in March.
The point of all this in the first weeks is not to find a fault. It is to have a normal, written down, in your own handwriting, before anything ever goes wrong. When something does change — and something eventually does — the question stops being "is this bad?" and becomes "is this different from my own days?" That is a far easier question to answer, and it is the one an installer can actually act on.
